1. Field of the Invention
This invention relates to semi-automatic woodworking machinery, in particular to machines for making miter joints, angle joints, or butt joints by means of joint nails as in the manufacture of picture frames, cabinet doors, door and screen frames, case goods, and deck assemblies.
Joint nails are widely used in the woodworking industry. They typically range from about 9.5 to 17.5 mm wide and from about 1.6 to 6.3 cm long, having a cross-section like that of a narrow I-beam. They are slightly tapered. The edges are sharp, and one end is sharp. Such joint nails, also called clamp nails, are driven into kerfs which are sawed into the surfaces to be joined.
Prior practice in furniture and picture-frame factories is to clamp the workpieces in a kerfing machine, the surfaces to be joined being separated a cm or so to clear the saw shaft and permit the entry of a kerfing saw. The saw is a small-diameter (e.g., 3 cm), high-speed rotary saw mounted on the shaft of an electric motor. The saw, or the work, is then moved in translation to cut the kerf in both workpieces at once. Kerfed workpieces are then moved in batches to a nailing machine. Here they are clamped with their kerfed surfaces in contact-- making a single kerf-- and a nailing head inserts a joint nail in the kerf, fastening the two workpieces together.
It is not economic to keep together the pairs of workpieces that were kerfed together; hence, the batches transferred to the separate nailing machine are random. Due to manufacturing variations in the thickness of workpiece stock, the outer surfaces of random pairs of nailed pieces are usually not precisely even, because the joint nails line up the kerfs, not the front or outer surfaces of the pieces. On occasion, the unevenness is great enough to cause rejects.
If, however, pairs of workpieces can be jigged with their outer or front surfaces aligned, then kerfed, and the same pieces nailed, the surface alignment will be independent of variations in stock thickness and the quality of the product improved. A combined kerfing and nailing machine can effect this improvement.
2. Prior Art
Separate kerfing machines and nailing machines are well known. My prior U.S. Pat. No. 3,597,142 shows a nailing machine suitable for use as part of the present invention. Other prior patents on joint nailing and nailing machines known to me are U.S. Pat. Nos.:
2,900,635 -- O'Kelley -- 3/1954 PA0 2,947,990 -- O'Kelley -- 12/1960 PA0 2,987,724 -- Ferguson -- 6/1961 PA0 2,991,477 -- Hoyle, Jr. -- 7/1961
I am not aware of any prior showings of a combined kerfing and nailing machine.